Correct option is A
Explanation-
A. EMT (Epithelial to Mesenchymal Transition) → IV "Epithelial cells making up the mesoderm of the early somatopleure undergo this transition and get included in mesenchyme cell pool."
EMT is a biological process during which epithelial cells lose their cell polarity and cell-cell adhesion and gain migratory and invasive properties to become mesenchymal stem cells. During vertebrate limb development, the epithelial cells of the somatopleure undergo EMT and contribute to the mesenchymal cell pool that forms the limb bud.
B. Mesenchyme → III "A loosely organized, mainly mesodermal embryonic tissue."
Mesenchyme refers to a type of loosely organized embryonic connective tissue, largely derived from the mesoderm. It consists of unspecialized, migratory cells that contribute to many developing structures, including limbs, bones, and cartilage.
C. AER (Apical Ectodermal Ridge) → II "The thickening of ectoderm at the apex of the developing limb."
AER is a thickened ectodermal region at the apex (tip) of the limb bud. It is essential for maintaining the underlying mesenchyme in a proliferative state and guiding limb outgrowth in the proximal-distal direction.
D. Progress Zone → V "The proliferative mesenchyme that fuels limb bud growth."
The progress zone lies just underneath the AER. It consists of highly proliferative mesenchymal cells that contribute to the lengthening of the limb. The position and timing of cells exiting this zone determine the type of structure they will become (e.g., humerus vs. radius).
E. ZPA (Zone of Polarizing Activity) → I "The cells found within the most posterior region of the limb bud."
The ZPA is a cluster of mesenchymal cells located in the posterior part of the limb bud. It secretes Sonic hedgehog (Shh) protein, which is critical for establishing the anterior-posterior axis (thumb-to-little finger direction).
F. Autopod → VI "The distal part of tetrapod limb."
The autopod is the distal-most region of the developing limb, which eventually forms the hands (forelimb) or feet (hindlimb). It includes structures like digits (fingers or toes).
Correct Answer:
Option a : A - IV, B - III, C - II, D - V, E - I, F - VI
